/Engine/Source/Runtime/Slate/Public/Framework/MultiBox/MultiBoxExtender.h
Applies any menu bar extensions at the specified extension point
void Apply ( [FName](API\Runtime\Core\UObject\FName) ExtensionHook, [EExtensionHook::Position](API\Runtime\Slate\Framework\MultiBox\EExtensionHook__Position) HookPosition, [FMenuBarBuilder](API\Runtime\Slate\Framework\MultiBox\FMenuBarBuilder) & MenuBarBuilder ) const